Protective device



April 1, 1958 R. H. METZ PROTECTIVE DEVICE Filed Jul 5. 1952 FORGING MACHINE mouonom HEAT- me COIL PULSES IN LINE 48 -Pu| sEs IN LINE 47 INVENTOR. RALPH H. METZ ATTORNEYS ire tats PRGTECTHVE DEVICE Ralph H. Meta, Wooster, Ohio, assignor to The Timhen Roller Bearing tCompany, Contain, @hio, a corporation of Ulric Application July 3, 1952, Serial No. 297,060

10 Claims, (Cl. film-10.61)

The present invention relates generally to the induction heating art, and more particularly to a novel protective device for continuous induction heating coils and the like, for interrupting the flow of energy to the heating coils when the speed of the material passing therethrough decreases below a predetermined minimum value.

in a continuous heating process wherein the induction heating coil is constantly energized, the rate of travel of the material through the coil determines the temperature to which the material is heated. (lonsequently, if the rate of travel of the material through the coil is too slow, or stops completely, the material may become too soft and cause considerable damage to the interior of the coil.

It is an object of the present invention, therefore, to provide a novel protective device for continuous induction heating coils and the like, for interrupting the transmission of energy to the heating means when the speed of the material passing therethrough decreases below a predetermined minimum value. More particularly, it is an object to provide such a device which includes means for producing two separate sets of electrical pulses, the time interval between the pulses being proportional to the speed of the material passing through the heating means, whereby, when the time interval between pulses is too great, the transmission of energy to the heating means is automatically and immediately interrupted.

Further objects and advantages of the present invention would be apparent from the following detailed description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is shown.

Briefly, the protective device includes two time-delay relays which have individual switch means connected in series, and means for producing two separate sets of electrical pulses and directing one set to each relay, the time interval between successive pulses being proportional to the speed of the material entering the heating coil, whereby, if the speed of the material decreases below a predetermined minimum valve, at least one of the switch means is immediately opened so as to interrupt the flow of energy to the heating coil.

in the drawings:

Fig. 1 is a schematic view of an induction-heating circuit including a protective device constructed in accrdance with the teachings of the present invention, one of the relays being shown in the open position as occurs when the speed of the material entering the coil decreases below the predetermined minimum value,

Fig. 2 is a diagrammatic illustration of the two sets of individual electrical pulses responsive to the speed of the material passing into the induction-heating coil, and

Fig. 3 is a schematic view of a portion of the protective device circuit showing a modified construction for producing the two separate sets of electrical pulses responsive to the speed of the material entering the coil or the like.

Referring to the drawing more particularly by reference numerals, indicates generally a protective device embodying the teachings of the present invention, shown 2,829,2Ztl Patented Apr. 1, 1%58 a; in association with an induction-heating coil 12 and a forg ing machine 14 for processing stock S.

The stock S can be in the form of elongated metal bars or tubes, or can consist of relatively short pieces previously cut into predetermined lengths, and is fed into the induction heating coil 12 by means of pinch rolls 15.

it is to understood that other types of heating devices may be employed, and that quenching equipment or other types of processing equipment can be used in place of the forging machine shown.

The protective device it includes a rotatably mounted shaft i6 which supports a Wheel 13 in frictional engageent with the stock 5 entering the induction coil 32.

Mounted on the shaft 16 is a shutter Ztl which contains a series of equally-spaced arcuate apertures 22.

A light source 24 is disposed adjacent the shutter 2% on one side thereof so as to direct a beam of light through the apertures 22;.

Disposed on the opposite side of the shutter is a lightsensitive tube 26 which is positioned to receive the light passing through the apertures 22.

The light-sensitive tube 26 is connected to an electrical relay 28 which includes a pivotally mounted switch member 3t, and opposed switch contacts 32 and 34, the switch member 3% being in engagement with either the switch contact 32 or the switch contact depending on whether the tube 26 is energized or de-energized.

Also included in the electrical circuit are two pneumatic time-delay relays 36 and 33, which include contact bars ail and 42, respectively, movable between a circuit-closing position and a circuit-opening position. The contact bars as and 42 are biased toward the circuit-opening position by the force of gravity and helper springs (not shown).

The switch member is connected to one side of a source of suitable electrical energy through a conductor 44-. The time-delay relays 36 and 33 are connected to the other side of the same energy source through a conductor 46, and are also connected to the contacts 32 and 34-, through conductors 47 and 4 8, respectively. Thus, current will pass through either the relay 36 or the relay 33, depending on the position of the switch member 30.

The induction heating coil 12 previously referred to is energized from a suitable power source through conductors 4 and 50 which contain a magnetic switch 52. for controlling the flow of current therethrough. The magnetic switch 52 includes a coil 53 and a pair of contact bars 54 which are biased toward the circuit-opening position by a spring 55. The coil 53 is connected to a suitable power source through conductors 56 and 57, the conductor 57 including the contact bars lit) and 42. Thus, the coil 53 is energized to move the contact bars 54 to the circuitclosing position and energize the induction-heating coil 12, only when both of the contact bars and 4-2 are in the circuit-closing position. As soon as either of the con- Operation As previously described, the stock S is moved into and through the induction heating coil 12 at a substantially uniform rate of speed by means of pinch rolls 15.

The wheel 1% bearing on the stock S drives the shaft 16 and the shutter 20 at a speed which is determined by the rate at which the stock S is being fed into the induction heating coil 12. Thus, if the passage of the stock S into the heating coil 12 were to be slowed down or completely stopped, for one reason or another, the rotation of the shutter 20 would also decrease in speed, or stop entirely.

During normal operation, with the stock S moving into and through the coil 12 at a substantially uniform rate of speed, the light rays from the light source 24 pass through the apertures 22 so as to intermittently fall on the lightsensitive tube 26. The apertures 22 and the spaces between them are preferably substantially equal in length so that the intervals of energization of the tube 26 are substantially of the same duration as the intervals of dc energization.

As the shutter 20 rotates and the tube 26 is alternately energized and ale-energized, the switch member 30 moves back and forth between the switch contacts 32 and 34 so as to provide two independent sets of electrical pulses in the conductors 47 and 48, the pulses in each circuit being 180 electrical degrees out of phase with the corresponding pulses in the other circuit. These pulses are shown diagrammatically in Fig. 2.

Thus, when the switch member 30 is brought into contact with the switch'contact 32 (Fig. l) by either the energization or de-energization of the tube 26, a surge or pulse of current starts flowing from one side of the power source through conductor 44, the switch member 30, the contact 32, the conductor 47, and through the coil of the pneumatic time-delay relay 36, and the conductor 46, back to the other side of the power source.

When the switch member 30 is moved from the contact 32 to the contact 34 due to the change in the state of the light-sensitive tube 26, the electrical pulse in line 47 is terminated and a separate electrical pulse is started in line 48 (Fig. 2).

The pneumatic time-delay relays 36 and 33 are biased toward the open position by the force of gravity and helper springs, as previously mentioned. These relays move the contact bars 40 and 42 into circuit-closing positions just as soon as they are energized, and hold them in this position for a predetermined time after being de-energized, the time delay being determined by the setting of the pneumatic time-delay means. The time delay is set so that both of the contact bars 4% and 42 will be maintained in circuit-closing position so long as the speed of the shutter 20 is greater than the predetermined minimum speed necessary for the safe passage of the stock S through the induction-heating coil 12.

However, if the speed of the shutter 20 drops below the predetermined minimum speed, or if it stops completely so that the switch member 30 remains in engagement with the contact 32 (Fig. 1), for example, the contact bar 4t? of the time-delay relay 38 will move to the open position when the coil of the relay 38 has been de-energized for the time interval for which the relay has been set.

As shown in Fig. 2, if the relay 38 is set for a time interval of one and one-half times the normal interval between successive pulses, the contact bar 40 will move to the circuit-opening position at the point indicated by the letter X.

When the contact bar 40 moves to the open position, it opens the electrical circuit to the magnetic switch 52, thereby de-energizing the coil 53 and permitting the spring 55 to open the contact members 54 and interrupt the flow of electrical energy to the induction-heating coil 12.

In Fig. 3, there is shown a modified form of pulse producing circuit, similar parts being identified by the same numerals used in Fig. 1, plus 100. Thus, number 30 of Fig. 1 becomes number 139 in Fig. 3.

In the modified construction shown in Fig. 3, a cam wheel 120 containing a plurality of evenly spaced protuberances 122 is substituted for the shutter 29.

A cam follower 126 is connected to a switch member 139 and is urged into engagement with the peripheral surface of the cam wheel 12d by a spring 127. Thus, as the cam wheel 12% is rotated, the cam member 126 is moved up and down so as to move the switch member 130 between contacts 132 and 134, responsive to the speed of the shaft 116, in a manner similar to that caused by the energization and de-energization of the light-sensitive tube 26.

Thus, it is apparent that there has been provided a novel protective device for continuous induction-heating coils and the like, which fulfills all of the objects and advantages sought therefor. So long as the stock S passes into and through the induction-heating coil 12 at the normal rate, the heating coil 12 is continuously energized. However, whenever the speed of the stock S drops below the predetermined minimum value, the energy to the induction-heating coil 12 is immediately interrupted to prevent the stock S from becoming too soft and damaging the coil. Also, Whenever the proper speed is resumed, the coil 12 is immediately energized.

It is to be understood that the foregoing description and the accompanying drawing have been given only by way of illustration and example, and that changes and alterations in the present disclosure, which will be readily apparent to one skilled in the art, are contemplated as within the scope ofthe present invention which is limited only by the claims which follow.

What is claimed is:

l. The combination of a heating device; means for transmitting energy to the heating device; means for moving material to be heated into the heating device; and means for interrupting the transmission of energy to the heating device when the speed of the material entering it decreases below a predetermined minimum value, including means for producing two separate sets of electrical pulses in which the time interval between successive pulses is proportional to the speed of the material.

2. The combination of a heating device; means for transmitting energy to the heating device; means for moving material to be heated into the heating device; and means for interrupting the transmission of energy to the heating device when the speed of the material entering it decreases below a predetermined minimum value, including means for producing two separate sets of electrical pulses, the pulses in one set being spaced electrical degrees from the corresponding pulses in the other set.

3. The combination of a heating device; means for transmitting energy to the heating device; means for moving material to be heated into the heating device; and means for interrupting the transmission of energy to the heating device when the speed of the material entering it decreases below a predetermined minimum value, including two time-delay relays each containing switch means movable between an open position and a closed position, means for producing two separate sets of electrical pulses in which the time interval between successive pulses is determined by the speed of the material, and means interconnecting the time-delay relays and the pulse-producing means for directing one set of pulses to each relay.

4. The combination of a heating device; means for transmitting energy to the heating device; means for moving material to be heated into the heating device; and means for interrupting the transmission of energy to the heating device when the speed of the material entering it decreases below a predetermined minimum value, including two time-delay relays each containing switch means movable between an open position and a closed position, the switch means moving to the closed position when the relay is energized and to the open position a predetermined time after the relay is de-energized, an electrical circuit associated with the energy transmitting means containing the switch means connected in series, means for producing two separate sets of electrical pulses in which the time interval between successive pulses is determined by the speed of the material, and means interconnecting the time-delay relays and the pulse-producing means for directing one set of pulses to each relay.

5. A device of the type described, comprising two time-delay relays each containing switch means movable between an open position and a closed position; an electrical control circuit containing said switch means connected in series; a rotatably mounted apertured shutter; a light source positioned on one side of the shutter so as to direct light through the apertures; a light-sensitive tube positioned on the other side of the shutter so as to receive the light passing through the apertures; means associated with the light-sensitive tube for producing two separate sets of electrical pulses responsive to the state of energization of the tube; and means interconnecting the timedelay relays and the pulse-producing means for directing one set of pulses to each relay.

6. A device of the type described, comprising two timedelay relays each containing switch means movable between an open position and a closed position; an electrical control circuit containing said switch means connected in series; a rotatably mounted cam member; a cam follower yieldably maintained in engagement with the cam member; means associated with the cam follower for producing two separate sets of electrical pulses responsive to the movement of said cam follower; and means interconnecting the time-delay relays and the pulse-producing means for directing one set of pulses to each relay.

7. In combination, a heating device; means for moving material into the heating device; two time-delay relays each containing switch means movable between an open position and a closed position; an electrical control circuit containing said switch means; means for producing two separate sets of electrical pulses responsive to the speed of the material entering the heating device; and means interconnecting the time-delay relays and the pulse-producing means for directing one set of pulses to each relay.

8. In combination, a heating device; means for transmitting energy to the heating device; means for moving material into the heating device; two time-delay relays each containing switch means movable between an open position and a closed position; an electrical circuit for controlling the transmission of energy to the heating device containing said switch means; means for producing two separate sets of electrical pulses responsive to the speed of the material entering the heating device; and means interconnecting the time-delay relays and the pulse-producing means for directing one set of pulses to each relay.

9. In combination, a heating device; means for trans mitting energy to the heating device; means for moving material into the heating device; two time-delay relays each containing switch means movable between an open position and a closed position; an electrical circuit for controlling the transmission of energy to the heating device containing said switch means; a rotatably mounted apertured shutter; means rotating said shutter responsive to the speed of the material entering the heating device; alight source positioned on one side of the shutter so as to direct light through the apertures; a light-sensitive tube positioned on the other side of the shutter so as to receive the light passing through the apertures; means associated with the light-sensitive tube for producing two separate sets of electrical pulses responsive to the state of energization of the tube; and means interconnecting the timedelay relays and the pulse-producing means for directing one set of pulses to each relay.

10. In combination, a heating device; means for transmitting energy to the heating device; means for moving material into the heating device; two time-delay relays each containing switch means movable between an open position and a closed position; an electrical circuit for controlling the transmission of energy to the heating device containing said switch means; a rotatably mounted cam member; means rotating said cam member responsive to the speed of the material entering the heating device; a cam follower yieldably maintained in engagement with the cam member; means associated with the cam follower for producing two separate sets of electrical pulses responsive to the movement of said cam follower; and means interconnecting the time-delay relays and the pulseproducing means for directing one set of pulses to each elay.

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